Gas streams often carry material entrained (for example dust or moisture) therein. In many instances, it is desirable to remove some or all of the entrained material from a gas flow stream. For example, air intake streams to engines for motorized vehicles, construction equipment or for power generation equipment, often include moisture or particulate material therein. The particulate material, should it reach the internal workings of the various mechanisms involved, can cause substantial damage thereto. The moisture can also damage equipment. It is therefore preferred, for such systems, to reduce the level of particulate material and moisture in the gas flow upstream of the engine or other equipment involved. A variety of air filter arrangements have been developed for such removal. In general, however, continued improvements are sought.